Certain aircraft are equipped with gust lock levers as a part of the throttle quadrant which can be pivoted from a stowed position into a fully upright and operationally deployed position so as to lock the aircraft's flight control surfaces to prevent damage from occurring while on the ramp due to wind gusts, e.g., due to meteorological conditions and/or engine thrust from nearby taxiing aircraft. The gust lock lever is also typically provided with a crossbar extending laterally across the throttle quadrant so as to prevent the individual throttles being advanced from their retarded position when the lever is in its upright operative position.
An intermediate position between the stowed position and the upright operative position is sometimes provided whereby the flight control surfaces are unlocked and the throttles can be advanced somewhat to allow for taxiing with less than full engine thrust while on the ground (thereby minimizing the effect of the aircraft's thrust on surrounding aircraft and/or personnel). Aircraft equipped with such a gust lock lever system will also understandably include a warning system to alert the flight crew that the crossbar of the gust lock lever is in an intermediate position which prevents the throttles from being advanced to a full engine thrust position. In such an arrangement, therefore, the crew may freely choose to ground taxi using the thrust of one engine and, if the warning system is overlooked may attempt takeoff with less than full engine thrust. Such an occurrence could of course have a potentially disastrous outcome if the flight crew does not realize that take-off is being attempted with less than full engine thrust.
In order to assist flight crew recognition that the gust lock lever is in the intermediate position, certain systems may employ a side stepped crossbar which prevents one of the throttles from advancing to the crossbar. In such arrangements, therefore, an attempt to advance both throttles to a full thrust condition will cause the throttles to assume an asymmetrically differential side-by-side position relative to one another. Such asymmetrical positioning of the thrust levers is therefore a tactile warning to the flight crew (who usually grips both throttle handles with a single hand) that the gust lock lever has not been fully stowed in preparation for aircraft take-off. However, after a predetermined number of flight hours, the crossbar needs to be inverted by maintenance personnel so that the step is associated with the other throttle to prevent undue wear on one engine due to continual taxiing demands. Such maintenance action of course means that the aircraft will be taken out of service while the maintenance action is performed.